The use of a single synthetic fluid jet to produce air flow is not unusual or novel. One such devices is shown in Glezer et al. U.S. Pat. No. 6,123,145. However, we have discovered that when an array of orifices are coupled to a single fluid chamber one can synchronize the ejection of a plurality of synthetic fluid jets to create a low profile flat fan that generates significant, predictable and substantial fluid flow within a system that can be used for efficient cooling of desired components. In addition by limiting fluid flow conditions to a laminar flow one can produce a high efficiency cooling device.
Traditionally, cooling equipment utilizes mechanical cooling device such as rotary fans. For example, in cooling electronic equipment within a cabinet enclosure a single fan or multiple fans can be used. The fans circulate the air within the enclosure to maintain a flow of cooler air across a component or components that need to be cooled. The flow of air across a component in the enclosure is intended to take advantage of Newton's Law of Cooling, which predicts that the amount of cooling, is related to the temperature differential between the flowing air and the component to be cooled. The amount of cooling obtainable within an enclosure, where fluid is circulated by a rotary fan, is dependent on various factors including the ability of the fan to move cooler air across a warmer surface of a component, which results in heat transfer from the warmer surface to the cooler air.
One limitation of using cooling device such as a fan within an enclosure is that the input electrical energy required to power the fan increases the amount of heat within the enclosure. Consequently, the heat produced by the fan must also be dissipated.
Another limitation of a cooling device, such as a fan, is the generation of turbulent air flow. Although the temperature differential between the cooling air and the component is related to the cooling efficiency, if the air flow is turbulent rather than laminar, it can result in significant inefficiencies in heat transfer and thus can significantly degrade the overall efficiency and thus effectiveness of the cooling system.
The use of a synthetic air or gas jet for cooling as to opposed to the use of a rotary fan circumvents many of the inherent problems associated with the use of rotary fans within an enclosure. For example, the aforementioned use of a rotary fan results in significant energy consumption within the cabinet, some of which is expended in the form of heat while a synthetic fluid jet generally adds little heat to the system. As a result, in a cooling system using a rotary fan the excess heat generated by the fan is typically compensated for by either adding more fans or supplying additional power to the fan. Unfortunately both methods of compensation increase the heat load to be dissipated.
In addition as a result of adding more rotary fans or increasing the flow rate the fluid flow paths inside the enclosure can become convoluted and asymmetric causing turbulent or slug flow conditions. The occurrence of turbulent flow or slug flow decreases the heat transfer efficiency. To overcome the decrease in efficiency as a result of turbulent or slug flow one usually supplies more power to the rotary fan system in an effort to increase the flow rate of the fluid within the enclosure chamber.
Thus, the increase in flow rate of fluid within a rotary fan system generally results in several detrimental effects. First, the heat generated in the cabinet increases because of the additional power supplied to the rotary fan. Second, turbulent or slug flow within the cabinet not only decreases the cooling efficiencies it can increase the airborne audible noise. In fact, turbulent fluid flow or slug flow within the cabinet can result in a substantial increase in the audible output of the enclosure as well as structure borne noise due to speaker like output of flat panels impinged by turbulent flow. Finally, the use of large rotary fans to provide cooling within an enclosure can result in high frequency vibrations within the enclosure, often resulting in a degradation of the expected life of the components.
With the present invention a flat fan generates an array of synthetic fluid jets that smoothly blend in to a larger synthetic fluid jet while maintaining laminar flow conditions. At the same time the flat fan array of the present invention requires little energy consumption, generates no audible noise and also produces no discernible vibration within the enclosure while efficiently transferring heat.